The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

AIRFLOW LIMITATION AND BRONCHIAL PROVOCATION TESTING.

Jack Wanger RRT RPFT, Richard Martin MD, Charles Irvin PhD. National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado.

It has been suggested by the European Respiratory Society, American Association for Respiratory Care, and others that the lowest limit of ventilatory function for bronchial provocation (BP) testing is an FEV_{1} value of 1.0 to 1.5 liters, or a percent predicted FEV1 value of 60 to 70%. Indeed, the American Thoracic Society only states "...those with moderate to severe impairments of lung function should be tested with caution. " The reasoning for these recommendations appears to be related more to impression than actual information. Yet, there are a few studies that have reported BP testing in small numbers of COPD subjects with severe airflow limitation. We questioned if BP testing could be performed safely in subjects with a starting FEV1 value < 1.5 liters and 60% of predicted. Methods: We retrospectively reviewed all methacholine and histamine BP tests performed on adults over the past 5 years in our laboratory. Tests that were included in the analysis had: (1) baseline FEV_{1} < 1.50 liters and 60% of predicted, (2) reproducible baseline FEV_{1} measurements, and (3) at least a 20% fall in FEV_{1} from the post-diluent FEV_{1}. We used the 5- breath dosimeter technique with doubling concentrations of the challenge agent. Results: We performed 4,531 tests from 1991 through 1995, with 83 studies (77 methacholine, 6 histamine) in 81 subjects meeting inclusion criteria. The mean±SEM baseline FEV_{1} was 1.32±0.017, range 0.64 to 1.49 L; baseline FEV_{1} percent predicted was 45.25±0.847%, range 22 to 59%; post-diluent FEV_{1} was 1.33±0.021, range 0.65 to 1.65 L; post-last dose of agonist was 0.97±0.018, range 0.40 to 1.35 L; post-bronchodilator FEV_{1} was 1.51± 0.038, range 0.62 to 2.73 L. There were 12 subjects with baseline FEV_{1} values between 1.0 and 1.2 liters, and 3 subjects with FEV_{1} values below 1.0 liters, and 10 subjects with a FEV_{1} percent predicted value o35%. In all 83 tests, a bronchodilator was administered when the test became positive (i.e., at least a 20% fall in FEV_{1}). In only 4 tests, we found that the subjects did not reverse to within 90% of their baseline FEV1 value. These 4 individual's reversibility values were 86, 85, 84 and 61% of their baseline FEV_{1} value. The results of repeat spirometry following a second bronchodilator treatment in these 4 subjects was not recorded, but we know from a review of the charts that none of these individuals needed further intervention. Conclusion: While there may be an occasional need to administer additional treatments, in 95% of the cases one bronchodilator treatment is adequate to reverse the effects of the challenge. Even in subjects with severe airflow limitation (i.e., FEV_{1} values of less than 1.5 liters and 60% of predicted) bronchial provocation testing with methacholine and histamine can be performed safely.

Reference: OF-96-066

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